You can change Android’s behaviour when you toggle airplane mode via adb commands.
Check current status:
adb shell settings get global airplane_mode_radios
# -> cell,bluetooth,wifi,nfc,wimax
adb shell content query --uri content://settings/global --projection name:value --where "name='airplane_mode_radios'"
The list of airplane_mode_radios defines which “radios” will get turned off
when airplane mode is turned on.
By removing from that list, you can keep the omitted radios on.
# Keep Wi-Fi on when turning on airplane mode:
adb shell settings put global airplane_mode_radios cell,bluetooth,nfc,wimax
# Keep both Wi-Fi and bluetooth on:
adb shell settings put global airplane_mode_radios cell,nfc,wimax
# Revert to default:
adb shell settings delete global airplane_mode_radios
There’s also a way to stop a device from turning on one of these radios when Airplane Mode has been enabled. By default, the options given to this command are WiFi, Bluetooth, and NFC.
adb shell settings put global airplane_mode_toggleable_radios bluetooth,nfc
# Revert to default:
adb shell settings delete global airplane_mode_toggleable_radios
Sources: See this answer, xda.